The present invention relates to a support pad for outdoor equipment and appliances and installation method that not only raises the unit to provide clearance from grade, as required by most building codes, but that also secures that unit to prevent movement and tipping associated with hurricane force winds.
Typically, an equipment pad, like those used for AC condensing units, is constructed of poured concrete formed in situ. This may be convenient when other concrete work is being performed on site, however, atypical installer would find mixing or purchasing concrete specifically for this small application to be impractical, time consuming, or expensive. A poured concrete pad also takes time to cure before heavy equipment can be placed on and fastened to it, further interrupting the installation process.
Prefabricated plastic and concrete pads are available as an alternative for transport and placement on site. Available plastic pads are typically lightweight and do not provide the required dead load to resist tipping due to high winds once equipment is mounted on the pad. Conventional hardware used to secure equipment to these relatively thin plastic pads may also be prone to pulling out of the plastic. Conversely, preformed solid concrete pads are heavy and difficult to handle. Other available pads are composed of a lightweight foam interior contained within a concrete shell, such as the “The Hurricane Pad™” manufactured by DiversiTech (Duluth, Ga.). As a result of their construction, these foam interior pads are prone to damage if dropped or mishandled. In many instances, foam-cored pads are too light to adequately secure an air conditioner in high winds.
A hurricane-wind rated equipment pad must be able to keep the equipment in place during high winds and also prevent the unit from toppling over or moving. The minimum necessary weight of the pad is dependent on the size and weight of the equipment and the wind speed. Hurricane-resistant equipment pads must survive wind speeds up to 180 mph, with the actual required wind speed dependent on the location.
As a demonstration, Table 1 below provides the minimum weight necessary for a 36 inch×36 inch pad to secure equipment of various sizes and weights. The wind load is calculated from the methods presented in American Society of Civil Engineers (ASCE) Standard 7-16. The equipment and pad are assumed to be a rigid structure resting on flat ground in a moderately open area. The dimensions and weights of the equipment listed in Table 1 are based on commercially available outdoor units used in split air conditioning (AC) systems and are representative of equipment that could be mounted to such pads. Modern, high-efficiency, AC outdoor units have become much taller to allow greater heat exchanger area on the same footprint, which has exacerbated the wind-driven tipping issue. For example, in Table 1 the Required Pad Weight increases from 148 pounds for a 24×24×30-inch-high outdoor unit to 519 pounds for a 32×32×50-inch-high outdoor unit atop a 4 inch tall pad in a 150 mph wind zone. Building codes also require a minimum of a 2 inch border around the perimeter of any equipment, so that a 32 inch base is the largest unit size that can be placed on a 36 inch pad.
TABLE 1Required equipment pad weight to resist tipping.Unit DimensionsRequired Pad WeightWidthLengthHeightWeight150 mph Wind180 mph Wind(in)(in)(in)(lb)(lb)(lb)242430100148257242435120206349262630120149266262635140213368282830140149276282835160219386282840190292505303030160149285303035190216395303040220297524303045240400682323235220213403323240250301543323245280403703323250310519883Table 1 makes clear that a concrete pad would need to be quite heavy to prevent tipping due to the moment caused by wind, making it very difficult to carry one into place at the installation site.
One known approach proposed the use of a hollow pad with a hollow interior chamber filled with sand, other granular materials, or water so as to achieve the necessary weight required to prevent the pad from tipping in hurricane-strength winds. With water, the pad was not intended to be completely filled so that in colder climates, the expansion of water as it freezes would not deform or damage the pad. Even if such a pad were completely filled with water and the height was increased to 6 inches, for certain tall outdoor equipment, the water alone would not provide sufficient weight to keep the pad in place in the highest possible wind zones, such as the 180 mph region of south Florida. The weight of the pad can be further increased with use of higher density fill materials such as sand, which is known in the art. At least one central support has also been proposed to prevent sagging, but that would limit the ability of a granular material, like sand, to completely fill the hollow core, reducing the fill volume and therefore the weight of the filled pad. If the central support is large, it can significantly reduce the volume of fill material available for weighing the pad down.
One object of our invention is to provide an easily-transportable, lightweight, rugged, and low-cost equipment mounting pad and installation method that, once located and leveled on site, can be secured to prevent theft and tipping, even in high wind loads. Our novel equipment pad can be configured as a hollow plastic shell that can be rotationally molded to reduce cost and minimize weight. If the pad is formed by conventional rotational molding, the molded pad will typically be formed from one of a variety of thermoformed plastics. The currently preferred embodiment uses a linear low-density polyethylene (LIDPE) to form a rigid structure with uniform wall thickness. However, any thermoform-capable material such as low-density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), cross linked polyethylene (XLPE), nylon, polypropylene, and polyvinyl chloride (PVC) are acceptable alternatives. While the currently preferred material wall thickness for the pad is 0.2 inches throughout the pad, alternative embodiments can use material thicknesses from 0.1 inches to 0.75 inches with, if desired to reduce costs, non-uniform wall thickness by using well known shielding on the rotational mold to adjust cooling times and thereby obtain non-uniform wall thicknesses. For example, the side-walls could be 0.1 inches, the top load bearing surface 0.5 inches and the bottom ground facing surface 0.2 inches. As pointed out herein, the adjustable securing slots in the pad provide support from deflection and can allow the load bearing surfaces to be thinner as well.
The empty shell, which contains a gelling formulation of known composition according to our invention, can be filled with water and sealed once at the installation site. The gel/solidus formed inside the pad will be used to prevent weight loss, even if the leak-tight seal is compromised. Additionally, if a super absorbent polymer (SAP), including but not limited to sodium polyacrylate, sodium polycarbonate, polyacrylamide copolymers, ethylene maleic anhydride, carboxymethylcellulose, polyvinyl alcohol copolymers, or polyethylene oxide, is used in the gelling compound formulation, then the resulting mixture will not expand upon freezing, thereby allowing the pad to be completely filled with water, avoiding the need for an expansion void space. Filling the interior volume completely also allows the gelled mixture to provide support to the pad, serving to prevent deformation and remove the need for any dedicated internal support structure.
In the event the filled equipment pad, according to our invention, did to provide sufficient weight to prevent tipping in the highest wind conditions, anchors can be screwed into the ground to add additional tipping resistance.
Our novel equipment mounting pad will be secured to the outdoor unit through easily adjustable securing straps that are installed into specially designed slots through the top of the pad. The securing straps are adjustable within the slots, able to rotate and slide inwards and outwards, to accommodate various sizes and shapes of equipment. These straps are cinched down to the pad and fastened to the unit to firmly secure the unit to the pad, preventing rocking, excessive vibration, and tipping. Additionally, extra slots and slots at various slot angles can be made available for use without departing from the scope of our invention. These slots also provide structural strength to the pad.
The equipment pad of our invention also contains a structure for anchoring the pad to the underlying support, whether soil, concrete, or other. Mount holes positioned near the perimeter of pad allow for the use of ground anchors or concrete fasteners and are positioned such that they can be installed with the unit in place. As stated earlier, anchoring the pad provides additional wind resistance, when needed, by holding the pad to the ground further preventing tipping or sliding of the unit and pad assembly.
The equipment pad of our invention contains a means for stacking multiple pads on top of one another and keeping them from sliding or shifting during storage and transportation. A protrusion on each corner of the equipment pad mates with a corresponding recess in the bottom of a pad placed on top of the former.
Equipment theft will be deterred due to the combined weight of the pad and the equipment, and if used, the lifting strength of the anchors installed into the underlying support. Moreover, our invention contemplates that the equipment can be connected to the pad with known types of anti-theft fasteners, such as one-way machine or sheet metal screws or those with unique heads that can only be removed with special tools. An anti-theft cable can also be installed. Similar to the securing straps, the anti-theft cable can connect to the pad using one of the unused slots.